1. Field of the Invention
This invention relates to an icebreaker system for marine platforms and to a platform equipped therewith, said plaform being of the weighted-base type or of the `jacket` type with multiple columns fixed to the ground by driven-in piers.
2. Description of the Prior Art
Oil exploration and extraction operations in waters lying near to or above the 70th parallel North pose very tricky problems in winter. For whereas the sea becomes clear or nearly so in summer, with numerous errant ice-floe residues, winter brings with it a line of ice which advances in relatively invariable directions. Thus, at the latitude of the Beaufort Sea, the ice is virtually unbroken `pack ice` advancing into the sea. The thickness of this sheet of ice is from about 3 meters to 9 meters, but in some places cliffs up to 30 meters high are formed when two sheets of ice thrust against each other. Indeed the movements of these nondefined ice floes implies relative motions which develop immense pressures and create upraised areas formed by the shattering and superimposition of excess material.
The whole ice system transits constantly with respect to a fixed point, though with occasional halts and resumptions of the movement and with changes of direction.
The methods at present used for setting up oil operations in a fixed area are of two kinds:
the first consists in creating a zone which is protected by a fairly high embankment having a slope such that the pack ice is raised as it moves over the slope and breaks up into pieces which transit more or less past the obstacle placed before them;
the second resorts to weighted-base conical platforms which, by a mechanism similar to that described precedingly, breaks up the sheet of ice as it rises over the slope opposing it.
The difficulty with both these methods stems primarily from the short time for which there is free access to the job sites. It is necessary for the work
dredging and the like--to be carried out during the period when the ice opens up, or else icebreakers have to be kept moving around the job site continually in order to prevent the latter from being disrupted by the arrival and movement of the ice floes. Despite the shallowness of the water in the regions of interest (10 to 50 meters), the solutions mentioned above call for fairly extensive and hence very costly excavation work.